Achieved serum samples of persons with or without evidence of COVID-19 infection are tested using the different commercial SARS-CoV-2 antibody immunoassays. The performance of the immunoassays is then assessed by comparing the 2 groups of samples.

Achieved serum samples of the different testing groups are retrieved and tested with the immunoassays according to manufacturer's instruction.

The test results are then compared and analyzed with statistical tests to assess the immunoassays'performance

Inclusion criteria for COVID-19 infected sera: any patient with PCR confirmed COVID-19 infection

Inclusion criteria for COVID-19 negative sera: sera collected after a negative SARS-CoV-2 PCR

Exclusion Criteria:

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Patients who attended clinic and had a positive SARS-CoV-2 PCR and subjects who had COVID-19 negative serum during the epidemic in Hong Kong.